在JS中添加表中的新行，如何包含变量？

I know I'm making a stupid mistake... but I started using ajax just an hour ago. I have a problem with variables in JS.

When i write +'id_komputery'+ then js return error : "Uncaught SyntaxError: missing ) after argument list". The same with id='id_komputery'

    $.ajax({
    url:'add.php',
    method:'POST',
    data:{
        producent_new:'producent_new',
        nazwa_new:'nazwa_new'
    },
    success:function()
    {
        var id_komputery = '<?= $id_komputery ?>';
        console.log(id_komputery);
        $("#main_table > tbody").append('<tr id='id_komputery' ><td width="50" align="center"><input type="checkbox" name="komp_id[]" class="delete_komputery" value='id_komputery' /></td><td width="50" align="center">+'id_komputery'+</td></tr>');
    }
});

Replace this line:

$("#main_table > tbody").append('<tr id='id_komputery' ><td width="50" align="center"><input type="checkbox" name="komp_id[]" class="delete_komputery" value='id_komputery' /></td><td width="50" align="center">+'id_komputery'+</td></tr>');

with this one:

$("#main_table > tbody").append('<tr id="' + id_komputery + '"><td width="50" align="center"><input type="checkbox" name="komp_id[]" class="delete_komputery" value='id_komputery' /></td><td width="50" align="center">'+id_komputery+'</td></tr>');

You are wrong in the column 'id_komputery'. It misses the concat operator You have to change this with:

'<tr id="' + id_komputery + '" >...'
'...<input type="checkbox" name="komp_id[]" class="delete_komputery" value="' + id_komputery + '" />'

Or with es2015+, you can use interpoller expression:

$("#main_table > tbody").append(`<tr id="${id_komputery}"><td width="50" align="center"><input type="checkbox" name="komp_id[]" class="delete_komputery" value="${id_komputery}" /></td><td width="50" align="center">${id_komputery}</td></tr>`);

You forgot to put "'" near +'id_komputery'+ '</td></tr>') (you have +'id_komputery'+ </td></tr>')) and javascript consider it as varaible and is invalid variable and you should not quote the vairable here +'id_komputery'+ this becomes simple string literal, instead you just write - id_komputery

$("#main_table > tbody").append('<tr id='id_komputery' ><td width="50" align="center"><input type="checkbox" name="komp_id[]" class="delete_komputery" value='id_komputery' /></td><td width="50" align="center">+'id_komputery'+'</td></tr>')

You are forgetting several quotes around the append line plus a minor change.

$("#main_table > tbody")
    .append('<tr id='id_komputery' >
        <td width="50" align="center">
            <input type="checkbox" 
                   name="komp_id[]" 
                   class="delete_komputery" 
                   value='id_komputery' />
        </td>
        <td width="50" align="center">+'id_komputery'+ 
        </td></tr>'
   );

Above is your syntax formatted.

Under is the syntax with the quotes fixed.

$("#main_table > tbody")
    .append('<tr id="id_komputery">
        <td width="50" align="center">
            <input type="checkbox" 
                   name="komp_id[]" 
                   class="delete_komputery" 
                   value="id_komputery"/>
        </td>
        <td width="50" align="center">'
            +id_komputery+
        '</td></tr>'
   );

I have corrected the your code. Replace the your code with below code:

$.ajax({
   url:'add.php',
   method:'POST',
   data:{
      producent_new:'producent_new',
      nazwa_new:'nazwa_new'
   },
   success:function()
   {
      var id_komputery = '<?= $id_komputery ?>';
      console.log(id_komputery);
      $("#main_table > tbody").append('<tr id="'+ id_komputery +'"><td width="50" align="center"><input type="checkbox" name="komp_id[]" class="delete_komputery" value="'+ id_komputery +'" /></td><td width="50" align="center">'+ id_komputery +'</td></tr>');
   }
});